The present invention relates to a feeding device for feeding an optical fiber from a coil and for recoiling unused fiber for use in an apparatus for measuring the temperature of a melt. The device according to the present invention comprises a support for a coil, a feeding mechanism for decoiling the optical fiber from the coil and recoiling the optical fiber, and at least one motor for driving the feeding mechanism. The present invention also relates to an apparatus for measuring the temperature of a melt, particularly of a molten metal, for example molten steel, with an optical fiber.
As known from EP 2 799 824 A1, an Electric Arc Furnace (EAF) process for the production of molten steel is a batch process made up of the following operations: furnace charging of metallic components, melting, refining, de-slagging, tapping and furnace turnaround. Each batch of steel, called a heat, is removed from the melting furnace in a process called tapping and hence, a reference to the cyclic batch rate of steel production is commonly a unit of time termed the tap-to-tap time. A modern EAF operation aims for a tap-to-tap cycle of less than 60 minutes and is more on the order of 35-40 minutes.
EP 2 799 824 A1 relates to a robotic immersion device for measuring the temperature in a metallurgical vessel using a molten metal immersed consumable optical fiber and immersion equipment capable of inserting a temperature device through the side wall of an EAF to a predictable molten steel immersion depth with a temperature-to-temperature measuring frequency of less than 20 seconds. The ability to sample on-demand, singularly or in rapid succession, allows a measuring strategy that can update a mathematical predictive model for EAF operations at key times during the process with the ability to measure in rapid succession providing near continuous temperature data at a low cost.
EP 2 799 824 A1 discloses providing a spot measurement rather than a continuous measurement. EP 2 799 824 A1 discloses a low cost solution for temperature measurements suitable to be utilized at a sufficiently high sampling frequency to meet the updating demands of the mathematical models of the EAF melting process, while solving the problems associated with immersed optical fiber in harsh environments. The solution provides a near continuous temperature measuring output comprised of immersing an optical fiber into the molten metal through the slag covering without first contacting the slag, maintaining a predetermined immersion depth during the measuring period by controlled feeding, protecting the non-immersed portion against devitfication in the high ambient heat of the EAF interior, removing and recoiling unused fiber after the measurement, measuring the bath level upon recoiling and an immersion equipment for repeating the measuring processes always duplicating the initial starting conditions.
Feeding the optical fiber, particularly a metal coated optical fiber, from the coil and recoiling unused fiber after the measurement may have the effect that the optical fiber becomes entangled for example due to an elastic spring back effect. For this reason, the feeding machine known from EP 2 799 824 A1 is adapted with additional means to avoid an elastic spring back effect from the coil or spool. The feeding machine comprises two servo motors or feeding motors to control the fiber movement. One feeding motor takes care of the de-coiling and recoiling of the fiber and pre-feeds fiber in such a way that the feeding motor can accelerate very fast.
An apparatus for automatically uncoiling a spool of wire is known from U.S. Pat. No. 4,742,973. An arrangement for facilitating the withdrawal of flexible material is known from U.S. Pat. No. 2,716,008. Temperature measurement systems for high temperature object employing an optical fiber are known from JP 9101206 A, JP 701 26 50 A and JP 9280958 A.
It is an objective of the present invention to avoid blockage when decoiling and recoiling a fiber from a coil of a feeding device for feeding an optical fiber.